Method and system for calibrating a virtual reality system

ABSTRACT

A virtual reality system includes a platform, a headset, a mount, and a control unit. The headset includes a motion-sensing unit and a display unit configured to display a video of a virtual environment. The mount is positioned on the platform and configured to releasably engage the headset. While the headset is engaged with the mount, the headset is positioned in a first position. While the headset is disengaged from the mount, the headset is positioned in a second position. The control unit is connected to the headset and configured to receive first data representing the first position and associate the first position with a predetermined first perspective of the virtual environment. The control unit is also configured to receive second data representing the second position, determine a second perspective of the virtual environment corresponding to the second position, and provide video of the virtual environment from the second perspective.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/163,313 filed May 18, 2015 which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

1. Field

This application relates generally to video-based virtual realitysystems and, more specifically, to systems and methods for aligning avirtual reality headset to calibrate a virtual reality system.

2. Description of the Related Art

Virtual reality is a computer-simulated environment that can simulate auser's physical presence in real or imaginary environments. Applicationsof virtual reality include medical, gaming, and military environments. Avirtual reality environment typically includes visual images displayedon a computer screen or through a stereoscopic (e.g., 3D) display. Forexample, video may be displayed on a wearable headset that provides animmersive virtual experience.

In some virtual reality applications, a user may change the displayedperspective of the virtual environment through the use of a keyboard,mouse, joystick, or other input device. In addition to or instead ofsuch conventional input devices, a wearable headset may incorporatemotion and/or orientation sensors that detect the position of theheadset. The orientation of the headset may correspond to a particularlook direction in the virtual environment, thus allowing a user tochange the displayed perspective of the virtual environment by movinghis/her head the same way he/she would look around the real world.

In some cases, it is desirable for the virtual environment to be alignedwith the real world such that a specific orientation of the headsetcorresponds to a particular look direction in the virtual environmentthat is consistent with what the user would expect. For example, a userfacing forward in a chair while viewing a virtual environment may expectto be looking forward in the virtual environment. Misalignment may causethe virtual perspective to be tilted or off-axis from the desired lookdirection. Small misalignments of only a few degrees may be perceptibleto a user. The misalignment may be distracting or disorienting and couldlead to undesirable effects, such as motion sickness.

Thus, there is a desire to be able to accurately align a virtual realityenvironment with a physical environment occupied by the user.

SUMMARY

The present disclosure describes a method and system for easily andconsistently calibrating a virtual reality system. The system includesat least one headset that displays a video of a virtual environment. Theperspective of a virtual environment is based on the position of theheadset. In some embodiments, one or more mounts are used to accuratelyalign the headset relative to a platform so that the orientation of thevirtual environment can be properly aligned with the platform based onthe mounted position of the headset. In some embodiments, a measuredposition of a platform is used to align the virtual environment with theplatform.

A method is provided for operating a virtual reality system having aplatform, a headset having a motion-sensing unit and a display unitconfigured to display a video of a virtual environment, and a mount,where the mount is positioned on the platform and the headset isreleasably engageable with the mount. In one embodiment, the methodincludes determining a first position of the headset while the headsetis engaged with the mount and associating the first position of theheadset with a predetermined first perspective of a virtual environment.The method also includes determining a second position of the headsetwhile the headset is disengaged from the mount, determining a secondperspective of the virtual environment corresponding to the secondposition of the headset, where the second perspective is based on thedifference between the first position and second position of theheadset, and displaying, using the headset, a video of the virtualenvironment from the second perspective. The video may include renderedanimated video.

In one embodiment, a virtual reality system includes a platform, aheadset, a mount, and a control unit. The headset includes amotion-sensing unit and a display unit configured to display a video ofa virtual environment. The mount is positioned on the platform. Themount is configured to releasably engage the headset. When the headsetis engaged with the mount, the headset is in a first position. When theheadset is disengaged from the mount, the headset is in a secondposition. The control unit is connected to the headset and is configuredto receive, from the headset, first data representing the first positionof the headset and associate the first position of the headset with apredetermined first perspective of a virtual environment. The controlunit is also configured to receive, from the headset, second datarepresenting the second position of the headset, determine a secondperspective of the virtual environment corresponding to the secondposition of the headset, where the second perspective is based on thedifference between the first position and second position of theheadset, and provide, to the headset, video of the virtual environmentfrom the second perspective.

In one embodiment, the mount is attached to a portion of the platform.The mount may be attached to a bench that is included in the platform.

In one embodiment, the position of the headset in the mount is orientedin a forward direction relative to the platform. In another embodiment,the position of the headset in the mount may be associated with aforward-looking perspective of the virtual environment. In yet anotherembodiment, the change between the first perspective and the secondperspective of the virtual environment is equal to the change in theorientation of the headset between the first position and the secondposition.

In some embodiments, a virtual reality system includes a platform; aheadset having a motion-sensing unit and a display unit configured todisplay a video of a virtual environment; a platform position-sensingunit configured to measure a position of the platform; and a controlunit connected to the headset and the platform position-sensing unit.The control unit is configured to: receive, from the platformposition-sensing unit, data representing a platform position; determinea frame of reference of a virtual environment based on the platformposition; receive, from the headset, data representing a position of theheadset; determine a relative headset position based on a differencebetween the platform position and the headset position; determine aperspective of the virtual environment in the frame of reference basedon the relative headset position; and provide, to the headset, video ofthe virtual environment from the determined perspective. In someembodiments, the video includes rendered animated video.

In some embodiments, the platform position corresponds to a forwarddirection of the platform and the forward direction of the platform isassociated with a forward-looking perspective of the virtualenvironment. In some embodiments, the difference between theforward-looking perspective of the virtual environment and thedetermined perspective of the virtual environment is equal to thedifference between the platform position and the headset position.

In some embodiments, the platform position-sensing unit is coupled tothe platform. In some embodiments, the platform includes a mountconfigured to engage the headset, and the platform position-sensing unitis coupled to the mount.

DESCRIPTION OF THE FIGURES

FIG. 1 depicts an exemplary embodiment of a virtual reality ride system.

FIGS. 2A-2B depict an exemplary virtual reality headset.

FIG. 3A depicts two users in a first position using the virtual realityride system.

FIG. 3B depicts a first exemplary perspective of a virtual environment.

FIG. 3C depicts a second exemplary perspective of the virtualenvironment.

FIG. 3D depicts two users in a second position using the virtual realityride system.

FIG. 3E depicts a third exemplary perspective of the virtualenvironment.

FIG. 4A depicts an exemplary virtual reality ride system with headsetalignment mounts.

FIG. 4B depicts the headset and alignment mount shown in FIG. 4A.

FIG. 5 depicts another exemplary headset alignment mount for the headsetshown in FIGS. 4A-4B.

FIG. 6 depicts another exemplary headset and alignment mount.

FIG. 7 depicts an exemplary process for calibrating and operating avirtual reality system.

FIG. 8 depicts another exemplary process for calibrating and operating avirtual reality system.

FIG. 9 depicts a block diagram of an embodiment of a virtual realitysystem.

FIG. 10 depicts a block diagram of another embodiment of a virtualreality system.

FIG. 11 depicts an exemplary computing system.

The embodiments depicted in the figures are only exemplary. One skilledin the art will readily recognize from the following discussion thatalternative embodiments of the structures and methods illustrated hereincan be employed without departing from the principles described herein.

DETAILED DESCRIPTION

The following description sets forth specific configurations,parameters, and the like. It should be recognized, however, that suchdescription is not intended to limit the present disclosure but isinstead provided as a description of exemplary embodiments.

FIG. 1 depicts an embodiment of a virtual reality ride system 100 thatincludes a platform 101 and virtual reality headsets 104 that displayvideo images of a virtual environment. Platform 101 may include physicalstructures associated with the virtual reality ride system 100, such as,for example, chairs, benches, mats, or the like. Platform 101 may alsoinclude a floor, walls, doors, windows, lights, or other features tocreate a surrounding structure associated with the virtual environment.In the embodiment depicted in FIG. 1, platform 101 includes seats 102 onwhich a user may sit while viewing the virtual environment through aheadset 104. The seat 102 may move by vibrating, rotating, translating,or the like, to provide physical sensations associated with eventsoccurring in the virtual environment.

FIGS. 2A-2B depict an enlarged view of an exemplary virtual realityheadset 104. Headset 104 includes a display/sensor portion 106 andstraps 108 to secure headset 104 to the user's head. The display/sensorportion 106 includes a display unit that generates a two-dimensional orthree-dimensional representation of the virtual environment. In someembodiments, the display unit may include a CRT, LEDs, LCDs, or thelike. Optics may be used to manipulate and condition the light from thedisplay to be presented to the user. The headset shown in FIG. 2B, forexample, includes binocular optics 110 for viewing the display.

Headset 104 may also include a position-sensing and/or motion-sensingunit that detects the position of the headset. Headset 104 may includesensors (such as gyroscopes, accelerometers, or the like) to tracktranslational movement in one, two, or three dimensions and to trackrotation about one, two, or three axes. While headset 104 is worn by theuser, the physical position of the user's head may be determined. Forthe purposes of this disclosure, position information may includelocation (e.g., linear position, such as the coordinates of an objectalong the x, y, and z axes of a rectilinear reference frame) and/ororientation (e.g., the angular position, the attitude, or the heading,elevation, and bank relative to a reference frame). Headset 104 may alsoinclude means for recalibration, such as a magnetometer to correct driftin gyroscopes used in headset 104.

It should be recognized that the techniques described herein may beapplied to or used in combination with other types of headsets. Asillustrated in FIGS. 2A-2B, headset 104 completely blocks the user'sfield of view of the surrounding environment. In some embodiments,however, the headset permits at least a partial view of thesurroundings, which may allow a user to maintain some visual awarenessof the surrounding environment.

As another example, the headset may be an augmented reality headset. Anaugmented reality headset typically provides a display without fullyblocking the user's field of view. An augmented reality headset maydisplay information, images, video, or other content that can be viewedat the same time as at least a portion of the surrounding environment.In some embodiments, an augmented reality headset includes a transparentdisplay or one or more cameras that provide video of the surroundings.In some embodiments, the content displayed by an augmented realityheadset supplements or enhances the surrounding environment. Anaugmented reality headset may include some or all of the featuresdescribed above with respect to virtual reality headset 104 (e.g., aposition-sensing and/or motion-sensing unit).

In exemplary virtual reality ride system 100, headset 104 is associatedwith a position in the virtual environment and displays a video image ofthe virtual environment from the perspective of its virtual position.The physical orientation of headset 104 may be mapped to a virtualorientation that determines the perspective of the virtual environmentfrom the virtual location. For example, the look direction of theperspective in the virtual environment may correspond to the physicalorientation of headset 104. The user may change the perspective or lookdirection by altering the orientation of the headset (e.g., by turning,tilting, raising, and/or lowering his/her head). When a user tiltshis/her head back, for example, headset 104 may display an image of thevirtual environment above the virtual location associated with headset104. Thus, the user may “look around” the virtual environment simply bymoving his/her head the same way he/she would look around the physicalenvironment, without the need for a separate controller or input device.

In addition, the virtual location associated with headset 104 may bebased on the physical location of headset 104. In some embodiments,headset 104 includes sensors to detect and track translational movement,allowing the user to change the virtual location associated with headset104 by leaning or moving around platform 101, thereby changing theorigin of the virtual perspective.

In some embodiments, the virtual environment may be aligned withplatform 101 such that a particular physical position (e.g., locationand orientation) with respect to platform 101 corresponds to apredetermined perspective of the virtual environment. The alignment mayensure that the perspective of the virtual environment displayed to theuser is consistent with what the user would intuitively expect to seebased on his/her physical position.

For example, in exemplary virtual reality ride system 100 depicted inFIG. 1, the direction parallel to the floor of platform 101 andperpendicular to the back cushion of seat 102 may correspond to theforward direction in the virtual environment, or more precisely, to thedirection in the virtual environment that represents the forwarddirection relative to the virtual location associated with headset 104.Thus, a user sitting upright in the seat 102 with his/her head orientedforward would be shown an upright perspective looking straight ahead inthe forward direction of the virtual environment. Furthermore, when thevirtual location associated with headset 104 is moved forward, the userwould perceive that he/she too is moving forward.

FIGS. 3A-3E depict an exemplary virtual reality system 300 in which thevirtual environment is aligned with a physical platform 301. FIG. 3Adepicts a front view of two users 306 and 308 next to each other facingforward relative to a platform 301. FIG. 3B depicts an exemplary view ofthe virtual environment displayed to user 306 by headset 304A. Thelocation of user 306 in the virtual environment (i.e., the virtuallocation associated with headset 304A worn by user 306) is determined bythe physical position of the headset worn by user 306. Since user 306 ison the left side of the platform 301 (from the perspective of the users)and facing forward, headset 304A displays a first-person perspective ofthe virtual environment from the driver's seat of the car (according toU.S. convention) looking out the front windshield of the car.

FIG. 3C depicts an exemplary view of the virtual environment displayedto user 308 by headset 304B. User 308 is physically located on the rightside of the platform 301, and therefore headset 304B displays aperspective from the front passenger seat of the car. Since user 308 isalso facing forward, headset 304B displays a view looking out throughthe front windshield.

FIG. 3D depicts user 306 with headset 304A turned toward user 308. Inthis position, user 306 is shown a perspective from the driver's seatlooking toward the passenger seat, and sees a virtual representation308V of user 308, as shown for example in FIG. 3E.

Accordingly, FIGS. 3A-3E illustrate that the users' locations andperspectives in the virtual environment correspond to the physicallocations and orientations of headsets 304A and 304B in the physicalenvironment.

However, if the virtual environment displayed to a user is not alignedwith the platform 301 as described above, the user's view of the virtualenvironment may be inconsistent with what the user would expect based onhis/her physical position. For example, misalignment may cause theperspective to be tilted or off-axis from the virtual forward direction,even though the user is upright and facing forward in relation to theplatform 301. Furthermore, if there is nothing in the virtualenvironment that indicates which direction is forward (e.g., theinterior of the car depicted in FIGS. 3B-3C and 3E), motion in thevirtual environment may be misperceived (e.g., forward movement in thevirtual environment may appear to be sideways motion or include asideways component).

Even small misalignments of a few degrees may be perceptible to a user.Inconsistency between the virtual perspective displayed to the user andthe perspective that the user expects to see based on his/her physicalposition may be distracting or disorienting and could lead toundesirable effects, such as motion sickness.

To reduce misalignment between the virtual and physical environments,the system may be calibrated when the headset is in a known positionrelative to the platform. In some embodiments, the position of theheadset is determined and associated with a predetermined virtualperspective. The predetermined virtual perspective defines the frame ofreference or orientation of the virtual environment with respect to thephysical environment. The alignment between the virtual environment andthe physical platform is therefore defined by the position of theheadset at the time of calibration.

Accordingly, the accuracy of the alignment between the platform and thevirtual environment depends on how accurately the headset is alignedwith the platform at the time of calibration. An alignment mount may beused to accurately and precisely align the headset with the platform.The mount may be attached to the platform such that it is aligned withand fixed in a known position relative to the platform.

FIG. 4A depicts an embodiment of a virtual reality system 400 withexemplary headset alignment mounts. System 400 includes platform 401,headsets 404, 414, and mounts 405, 415. Mounts 405, 415 are placed inknown positions relative to platform 401. In FIG. 4A, mounts 405, 415are positioned on platform 401. Mounts 405, 415 may be fixedly orreleasably attached to platform 401. In FIG. 4A, mounts 405, 415 areattached to the backs of benches 402, 412. It should be recognized,however, that there are various places in which mounts 405, 415 may beplaced—including, for example, underneath a seat or bench, on theheadrest of a seat or bench, or on a pole, stand, rack, or the like. Itshould also be recognized that a mount does not necessarily need to beattached to a platform. In some embodiments, a mount is in a known, butremote, position relative to a platform.

FIG. 4A also shows headsets 404, 414 engaged with mounts 405, 415.Headsets 404, 414 are releasably engageable with mounts 405, 415 so thatusers sitting on benches 402, 412, for example, may use headsets 404,414 located in front of them. For example, a user sitting on bench 412may use headset 404 by disengaging it from mount 405.

FIG. 4B shows an enlarged view of headset 404 and mount 405 with headset404 disengaged from mount 405. Mount 405 and headset 404 are configuredto be complementary, such that headset 404 is in a known positionrelative to mount 405 when engaged with the mount 405. Mount 405conforms to the size and shape of headset 404 so that the position ofheadset 404 is limited when it is properly engaged with mount 405, butheadset 404 can still be easily engaged and disengaged. In someembodiments, a mount may not support or be configured not to engage aheadset unless it is properly positioned. In such cases, engagement ofthe headset with the mount indicates that the headset is in the correctposition.

Thus, when properly engaged with mount 405, the position of headset 404relative to mount 405 is known precisely. Furthermore, since theposition of mount 405 is known relative to platform 401, the position ofheadset 404 relative to platform 401 is also known.

It should be recognized that various mount geometries may be possiblefor a particular headset. For example, FIG. 5 depicts another exemplaryembodiment of a mount 505 that may be used with headset 404. Thegeometry of the mount may also vary based on the size and shape of theheadset. FIG. 6 depicts yet another exemplary embodiment of a mount 605that conforms to the geometry of a headset 604, which has a differentshape than headset 404. Depending on the geometry of the mount and theheadset, there are various ways in which the headset may be configuredto engage the mount, including being placed on, connected to, hung from,or inserted into the mount. Also, in some embodiments, the mountincludes hooks, clips, pegs, or other means for releasably engaging theheadset. In some embodiments, the headset includes hooks, clips, pegs,or other means for releasably engaging the mount.

In some embodiments, a mount is configured to engage more than oneheadset. For example, a mount may include a rack, stand, or otherstructure configured to engage multiple headsets for calibration. Forexample, in the example depicted in FIG. 4A, instead of mounts 405 and415, system 400 may include a rack configured to hold headsets 404, 414,which is positioned on or near the side of platform 401 so that userscan grab headsets 404, 414 upon entering platform 401.

FIG. 7 depicts a flow chart illustrating an exemplary process 700 forcalibrating and operating a virtual reality system using a mount. Thesystem includes a mount positioned on a platform and a headset that isreleasably engageable to the mount.

In step 702, a first position of the headset is determined when theheadset is engaged with the mount. The first position of the headset maybe determined based on measurements of the location and/or orientationof the headset. The measurements may be obtained by position or motionsensors provided in the headset.

In step 704, the first position of the headset is associated with afirst perspective of a virtual environment. Associating the firstposition with the first perspective sets the frame of reference of thevirtual environment. In some embodiments, the first position (i.e., theposition of the headset in the mount) is oriented to match a known state(e.g., a known frame of reference or orientation) in the virtualenvironment. For example, the first perspective may be predetermined sothat the position of the headset in the mount corresponds to aperspective that establishes a frame of reference for the virtualenvironment that aligns with the platform. The headset may send datarepresenting the first position to processors included in the virtualreality system to be associated with the first perspective of thevirtual environment.

The desired alignment between the platform and the virtual environmentmay be determined in advance of operating the system. The firstperspective depends on the position of the headset in the mount and ischosen such that the headset will display a perspective that isintuitively consistent with the position of the headset relative to theplatform. The mounts allow the headsets to be accurately aligned withthe platform so the first virtual perspective can be associated with theproper physical position. By knowing the position of the headsetrelative to the platform, the virtual environment may be aligned withthe platform by associating the position of the headset with the virtualperspective that results in the desired alignment. The greater theaccuracy with which the mount and headset are aligned to the platform,the better the alignment of the virtual environment will be.

It should be recognized that, for the purposes of calibration, theparticular position of the headset while in the mount is unimportant,provided the position is known and the system associates the mountedposition with the proper virtual perspective. In the embodiment depictedin FIG. 4A, the position of headset 404 in mount 405 is oriented in aforward direction relative to platform 401. However, in FIG. 5,exemplary mount 505 is configured such that the front of headset 404 isoriented in a downward direction when placed in mount 505. In this case,the orientation of headset 404 at the time of calibration would bemapped to a perspective of the virtual environment looking directlydown. FIG. 5 also illustrates that it may be possible to achieve themount characteristics discussed above with different mountconfigurations.

In step 706, a second physical position of the headset is determinedwhen the headset is disengaged from the mount. In one embodiment, theheadset is disengaged from the mount and positioned on a user's head toview images of the virtual environment. As discussed above, the positionof the headset may be determined by sensors included in the headset thatdetect the motion of the headset.

In step 708, a second perspective of the virtual environmentcorresponding to the second headset position is determined. The secondperspective may be determined based on the second position of theheadset determined in step 706. For example, second perspective may bebased on the difference between the first position and the secondposition of the headset. In one embodiment, the change in orientation orlook direction from the first virtual perspective to the second virtualperspective is based on the change in orientation of the headset fromthe engaged position to the disengaged position. For example, the lookdirection in the virtual environment may be moved from the lookdirection of the predetermined perspective by the same amount and in thesame direction as the orientation of the headset from its mountedposition to its updated position.

In step 710, video showing the virtual environment from the secondperspective determined in step 708 is displayed by the headset. In oneembodiment, the video includes animated images rendered based on thedetermined perspective of the virtual environment and thus the positionof the headset.

Returning to FIG. 4A, techniques for aligning a virtual reality systemusing a measured position of a platform will now be described. System400 includes a platform position-sensing unit 420 that detects theposition and/or motion of platform 401. Platform position-sensing unit420 may include sensors (such as gyroscopes, accelerometers, or thelike) to track translational movement of platform 401 in one, two, orthree dimensions and/or to track rotation of platform 401 about one,two, or three axes. System 400 may also include means for recalibrationof the sensors, such as a magnetometer to correct drift in gyroscopesused in platform position-sensing unit 420. In some embodiments, thesensor is located in, or attached to, platform 401. For example, thesensor may be located in bench 402 or 412, mount 405 or 415, orelsewhere on or in platform 401. In some embodiments, there is one ormore platform position-sensing unit. In some embodiments, each mountincludes a separate platform position-sensing unit.

The measured position of a platform can be used to keep the virtualenvironment aligned with the platform. This may be advantageous forsystems in which the orientation of the virtual environment is to remainfixed relative to the platform but the platform is likely to move, suchas in a plane, car, or other vehicle. For example, even if a headsetremains stationary relative to a platform, rotation of the platformitself can cause the headset to rotate, which changes the view of thevirtual environment. Thus, movement of the platform alters the displayedview just as if the user has turned his/her head, even if the user hasnot done so. Thought of another way, platform motion can cause theorientation of the virtual environment to drift and become misalignedwith the platform (e.g., the forward direction of the platform no longeraligns with the forward-looking direction in the virtual environment).This effect may be undesirable, particularly for applications in whichthe view of the virtual environment is to be controlled solely by theuser or should remain aligned with the platform. For example, an airlinepassenger viewing a movie in virtual reality would likely prefer thatthe view of the movie remain aligned with his/her seat rather thanchanging as the plane turns.

In some embodiments, a position of the platform is used to maintainalignment between the virtual environment and the platform. For example,platform position-sensing unit 420 can measure the position of platform401 and determine a relative forward direction based on the direction inwhich platform 401 is facing. System 400 can then be calibrated bysetting the frame of reference of the virtual environment to align withthe relative forward direction. Once calibrated, the views displayed byheadsets 404, 414 are based on their positions relative to the forwarddirection. Accordingly, instead of calibrating a system based on a knownposition of a headset in a mount as described above, the system iscalibrated based on the measured position of the platform.

In some embodiments, the system is re-calibrated periodically (e.g.,every second). Optionally, the frequency of re-calibration depends on anexpected motion of the platform (e.g., a system with a platform that isexpected to move or turn more quickly is re-calibrated more frequently).In some embodiments, the frequency of re-calibration depends on themeasured motion of a platform (e.g., re-calibration is performed morefrequently when rapid changes in platform position are detected toreduce the amount of drift).

FIG. 8 depicts a flow chart illustrating an exemplary process 800 forcalibrating and operating a virtual reality system using a measuredposition of a platform. The system may be, for example, system 400described above or system 800 or 900 described below.

In step 802, a position of a platform is determined. The position may bebased on a measurement by a platform position-sensing unit such asdescribed above. In step 804, a frame of reference of a virtualenvironment is determined based on the platform position. For example,the frame of reference may be oriented such that a predetermined virtualdirection (e.g., a forward-looking direction) is aligned with aforward-facing direction of the platform. In step 806, a position of theheadset is determined. The position of the headset may be measured asdescribed above with respect to step 702 in process 700. In step 808, arelative headset position is determined with respect to the platformposition. For example, the relative headset position may be thedifference between the measured headset position and the position of theplatform. In step 810, a perspective of the virtual environment in thereference frame is determined based on the relative headset position.For example, the perspective may deviate from the forward-lookingdirection in the virtual environment by the same amount that the headsetposition deviates from the platform position. In step 812, a video ofthe perspective of the virtual environment is displayed.

It should be recognized that some features of processes 700 and 800 maybe combined, the order of some features may be changed, and somefeatures may be omitted. It should also be recognized that processes 700and 800 may be applied to systems configured for one or more users.Also, the virtual reality systems and processes described above are notlimited to any particular virtual environment. For example, a virtualreality experience may include a walk through a city, a ride on Santa'ssleigh to the North Pole, flying on the back of an imaginary creaturethrough the sky, driving a jeep through a safari, or other real orimaginary virtual experiences.

The alignment and calibration techniques described herein may be appliedto other types of virtual reality systems besides rides, includinginteractive systems such as video games, simulators (e.g., flight andvehicle simulators), or the like. These systems may not include adedicated platform or bench, such as those described above. For example,a headset alignment mount may be attached to a personal desk, chair,monitor, or other object to align a headset used with a gaming console,personal computer, or the like. In which case, the object serves as theplatform to which the virtual environment is aligned.

Turning now to FIG. 9, an exemplary architecture of a virtual realitysystem 900 is described. Virtual reality system 900 may be used toimplement some or all of the operations of processes 700 and 800described above. FIG. 9 depicts a block diagram of an embodiment ofvirtual reality system 900, which includes platform 901, control unit902, headsets 904, mounts 905, and platform position-sensing unit 910.Control unit 902 includes workstations 906 and server 908. Each headset904 is releasably connectable to a mount 905 (as indicated by the dashedconnecting lines) and is connected to a workstation 906. Eachworkstation 906 is connected to server 908, which networks togetherworkstations 906 and platform position-sensing unit 910. Workstations906 and/or server 908 may be remote from platform 901 or integrated withplatform 901, for example, beneath a seat or in a cabinet.

In one embodiment, headsets 904 communicate data representing thephysical location and orientation of headsets 904 to workstations 906,which may pass the data to the server 908. Workstations 906 may includeone or more processors for rendering animated video or content of avirtual environment. Each workstation 906 renders a view of the virtualenvironment based on the virtual position associated with itscorresponding headset 904 (which is based on the physical position ofheadset 904), and provides the video to its corresponding headset 904.Server 908 may also include one or more processors to coordinate theworkstations 906 and provide data for rendering. The data may includeelements or events in the virtual environment such as, for example,scenery, characters, objects, character motion, or the like.

In an alternative embodiment depicted in FIG. 10, virtual reality system1000 includes a control unit 1002 having rendering processors 1006 and aserver 1008 similar to system 900, but headsets 1004 are connecteddirectly to the server 1008 rather than rendering processors 1006.Server 1008 may distribute animation video rendering processing amongrendering processors 1006, and then provide the rendered video to theappropriate headset. Notably, the number M of rendering processors 1006does not necessarily equal the number N of headsets 1004.

Although not shown, various alternative configurations are possible forreceiving communications from the platform position-sensing unit. Insome embodiments, the platform position-sensing unit communicates via awired or wireless communication link. In some embodiments, the platformposition-sensing unit communicates directly with one or more headsets orone or more workstations or rendering processors.

It should be recognized that some or all of the techniques describedabove for virtual reality systems can be applied in an analogous mannerto an augmented reality system. An augmented reality system may displaycontent based on the position of an augmented reality headset. Forexample, instead of, or in addition to, a virtual environment, a systemmay display information or other content associated with the surroundingenvironment. Furthermore, the system may determine the content to bedisplayed based on the position of the headset in a manner analogous tothe way in which the virtual reality systems described above determinethe perspective of the virtual environment to be displayed. If thecontent to be displayed by the augmented reality system depends on theposition of the headset, it may therefore be advantageous to calibratethe headset according to one or more of the techniques described above.

FIG. 11 depicts components of an exemplary computing system 1100configured to perform any one of the above-described processes. In someembodiments, the workstations, rendering processors, and/or serversdescribed above may include some or all of the elements of computingsystem 1100. Computing system 1100 may include, for example, aprocessor, memory, storage, and input/output devices (e.g., monitor,keyboard, stylus, drawing device, disk drive, Internet connection,etc.). However, computing system 1100 may include circuitry or otherspecialized hardware for carrying out some or all aspects of theprocesses. In some operational settings, computing system 1100 may beconfigured as a system that includes one or more units, each of which isconfigured to carry out some aspects of the processes in software,hardware, or some combination thereof.

In computing system 1100, the main system 1102 may include a motherboard1104 with a bus that connects an input/output (“I/O”) section 1106, oneor more central processing unit (“CPU”) 1108, and a memory section 1110,which may have a flash memory card 1112 related to it. Memory section1110 may contain computer-executable instructions and/or data forcarrying out at least portions of processes 700 and 800. The I/O section1106 may be connected to display 1124, a keyboard 1114, a disk storageunit 1116, and a media drive unit 1118. The media drive unit 1118 canread/write a non-transitory, computer-readable storage medium 1120,which can contain programs 1122 and/or data.

At least some values based on the results of the above-describedprocesses can be saved for subsequent use. Additionally, anon-transitory, computer-readable storage medium can be used to store(e.g., tangibly embody) one or more computer programs for performing anyone of the above-described processes by means of a computer. Thecomputer program may be written, for example, in a general-purposeprogramming language (e.g., Pascal, C, C++, Java, or the like) or somespecialized application-specific language.

The foregoing descriptions of specific embodiments have been presentedfor purposes of illustration and description. They are not intended tobe exhaustive or to limit the scope of the claims to the precise formsdisclosed, and it should be understood that many modifications andvariations are possible in light of the above teaching.

We claim:
 1. A virtual reality system comprising: a platform; a headsethaving a motion-sensing unit and a display unit configured to display avideo of a virtual environment; a mount positioned on the platform,wherein the mount is configured to be releasably engageable with theheadset, wherein the headset is in a first position when engaged withthe mount, and wherein the headset is in a second position whendisengaged from the mount; and a control unit connected to the headset,the control unit configured to: receive, from the headset, first datarepresenting the first position of the headset; associate the firstposition of the headset with a predetermined first perspective of thevirtual environment; receive, from the headset, second data representingthe second position of the headset; determine a second perspective ofthe virtual environment corresponding to the second position of theheadset, wherein the second perspective is based on the differencebetween the first position and second position of the headset; andprovide, to the headset, video of the virtual environment from thesecond perspective.
 2. The system of claim 1, wherein the first positionof the headset is oriented in a forward direction relative to theplatform.
 3. The system of claim 1, wherein the first position of theheadset is associated with a forward-looking perspective of the virtualenvironment.
 4. The system of claim 1, wherein the difference betweenthe first perspective of the virtual environment and the secondperspective of the virtual environment is equal to the difference in theorientation of the headset between the first position and the secondposition.
 5. The system of claim 1, wherein the mount is attached to aportion of the platform.
 6. The system of claim 5, wherein the platformincludes a bench, and the mount is attached to the back of the bench. 7.The system of claim 1, wherein the video includes rendered animatedvideo.
 8. The system of claim 1, wherein the video provided to theheadset includes augmented reality content, and wherein the augmentedreality content is based on the second position of the headset.
 9. Amethod of operating a virtual reality system, the system including aplatform, a headset having a motion-sensing unit and a display unitconfigured to display a video of a virtual environment, and a mount,wherein the mount is positioned on the platform and the headset isreleasably engageable with the mount, the method comprising: determininga first position of the headset while the headset is engaged with themount; and associating the first position of the headset with apredetermined first perspective of a virtual environment; determining asecond position of the headset while the headset is disengaged from themount; determining a second perspective of the virtual environmentcorresponding to the second position of the headset, wherein the secondperspective is based on the difference between the first position andsecond position of the headset; and displaying, using the headset, avideo of the virtual environment from the second perspective.
 10. Themethod of claim 9, wherein the first position is oriented in a forwarddirection relative to the platform.
 11. The method of claim 9, whereinthe first position of the headset is associated with a forward-lookingperspective of the virtual environment.
 12. The method of claim 9,wherein the difference between the first perspective and the secondperspective of the virtual environment is equal to the difference in theorientation of the headset between the first position and the secondposition.
 13. The method of claim 9, wherein the mount is attached to aportion of the platform.
 14. The method of claim 13, wherein theplatform includes a bench, and the mount is attached to the back of thebench.
 15. The method of claim 9, wherein the video includes renderedanimated video.
 16. The method of claim 9, wherein the video displayedusing the headset includes augmented reality content, and wherein theaugmented reality content is based on the second position of theheadset.
 17. A non-transitory computer-readable storage mediumcomprising computer-executable instructions for operating a virtualreality system, the system including a platform, a headset, and a mount,wherein the mount is positioned on the platform, and the headset isreleasably engageable with the mount, the computer-executableinstructions comprising instructions for: determining a first positionof the headset while the headset is engaged with the mount; andassociating the first position of the headset with a predetermined firstperspective of a virtual environment; determining a second position ofthe headset while the headset is disengaged from the mount; determininga second perspective of the virtual environment corresponding to thesecond position of the headset, wherein the second perspective is basedon the difference between the first position and second position of theheadset; and displaying, using the headset, a video of the virtualenvironment from the second perspective.
 18. The computer-readablestorage medium of claim 17, wherein the first position of the headset isassociated with a forward-looking perspective of the virtualenvironment.
 19. The computer-readable storage medium of claim 17,wherein the difference between the first perspective and the secondperspective of the virtual environment is equal to the difference in theorientation of the headset between the first position and the secondposition.
 20. The computer-readable storage medium of claim 17, whereinthe video includes rendered animated video.
 21. The computer-readablestorage medium of claim 17, wherein the video displayed using theheadset includes augmented reality content, and wherein the augmentedreality content is based on the second position of the headset.